Methanol fuel cells promise to provide efficient and low-cost electrical current from methanol without burning the fuel. Therefore, pollution from combustion is not created by the use of such fuel cells. The fuel cells can be at least as efficient as gasoline engines; they run cool, without the need for insulation and structural reinforcement; and rely on a relatively inexpensive fuel. The methanol fuel cells which were designed initially produced about 100 W, running up to 200 continuous hours, and up to 3,000 intermittent hours, without suffering any loss in performance. The goal is to produce units which can generate up to 40 kW, which would be enough to power a full-size automobile, and which can run for at least 1,000 continuous hours.
The biplate is a two-sided component which is placed between the membrane electrode assemblies (MEAs) in a fuel cell stack. One side of the biplate is oriented to face the anode of one MEA, and the other side of the biplate is oriented to face the cathode of another MEA. The biplate provides electrical contact to the MEAs. It also acts to separate air or oxygen provided to the cathode of one MEA and the fuel provided to the anode of the other MEA. As such it forms part of the fuel cell compartment containing either fuel or air.
The endplate is a fuel cell component which forms part of the last fuel cell compartment in a stack, if a stack is present. If the cells are not stacked, the endplate is simply a wall of the fuel cell. The endplate provides electrical contact between an electrode of the fuel cell and the electrical load which spans the fuel cell or stack of fuel cells. The endplate is simply a single-ended biplate. Thus, both fuel cell components, biplates and endplates, are conductive elements.
Typical biplates and endplates are made of a graphite/polymer composite. The polymer is a polymer binder which has the functional effect of making the biplate an extremely hydrophobic surface.
At this time, cost is the major factor limiting methanol fuel cell commercialization. One difficulty in the operation of methanol fuel cells is the water that normally accumulates in the channels of the cathode side of the biplate. The source of this water can be from the chemical reaction of the fuel cell, it can be a result of electroosmosis from the anode side, or it can be a result of simple diffusion. If the accumulated water is not removed, the performance of the fuel cell can suffer. The traditional way to remove this accumulated water has been by pressurized air.
It is desirable to design fuel cell systems which work at temperatures between 25 and 45.degree. C. However, the power output of methanol fuel cells at 25.degree. C. is only about 15-20% of the same cell operating at 90.degree. C. Thus, it becomes important to reduce the energy consumption of ancillary processes as much as possible. For example, power consumption of a pressurized air delivery system can unacceptably diminish the advantages of a room temperature methanol fuel cell. It is considered desirable to design such cells so as to minimize the air flow required to remove accumulated water.